Known roll forming machinery usually has a plurality of sets of roll dies, typically arranged in upper and lower matching pairs, and usually spaced apart along the length of the machine on roller stands. Typically, the roller dies at one stand will produce a continuous formation in the web, and the roller dies of the next stand will produce another formation, or for example increase the angle of the formation which has already been started at the previous stand and so on.
A wide variety of commercial and other products are made on such roll forming machines, such as roof decking siding, as well as a large number of components for consumer equipment. The shapes may simply be webs with edge formations formed along one edge or both, or may be C sections or U sections but in many cases consist of relatively complex formations with longitudinal formations being formed along the length of the web, side by side.
Generally speaking at each stand of rolls there are two lower dies and two upper dies arranged in pairs, on either side of a central web axis to form thereby various bends or shapes in the web. The lower dies engage the underside of the web and the upper dies engage the upper side of the web. The dies have circular shapes, and are mounted on rotatable axles so that the dies can rotate at the same speed as the sheet metal. A gear drive mechanism is coupled to the dies so as to drive them at the speed of the sheet metal.
In order to keep capital costs low, it is desirable to use the same roller dies for forming finished products from webs of varying widths. Thus, spacing between opposing roller die stands may need to be increased or diminished according to the width of the web being formed. In the past, each of the stands situated on either side of the web would have to be manually moved further apart, or closer together, to account for the width of the new web to be processed. However, as will be readily appreciated, it was time consuming to manually dismantle the arrangement of dies for one web width, and then reassemble the dies with a greater or lesser number of rolls between them to suit the new web width.
Commonly assigned U.S. Pat. No. 6,647,754, titled “Variable Width Roll Forming Apparatus”, herein incorporated by reference in its entirety, discloses several embodiments of a roll forming machine that is capable of quickly moving groups of roller stands, on either side of a metal web, either farther apart or closer together to accommodate webbing of differing widths.
In a preferred embodiment disclosed by U.S. Pat. No. 6,647,754, as shown in FIG. 1, a variable width roll forming apparatus, having an upstream end U and a downstream end D, includes opposed groups of upper and lower roller die pairs arranged on a base B. Each lower roller die is mounted through a collector plate within a sleeve that is mounted in a side plate. The lower roller dies are capable of axial and rotary movement within the sleeves, and the sleeves are axially movable relative to the side plates. Matching groups of upper roller dies are mounted through adjustment blocks that are bolted to the collector plates. Each collector plate is mounted on guide pins and bushings extending orthogonally from the corresponding side plate, and is movable toward and away from the corresponding side plate by operation of a jack screw against an internally-threaded fitting of the collector plate, whereby the distance between opposing pairs of collector plates can be easily adjusted. As is commonly accepted in the art, while the jack screw exerts force on the collector plate orthogonal to the side plate, the bushings and guide pins support the collector plate against forces transverse to the jack screw axis and parallel to the side plate. This distribution of transverse forces away from the jack screw is generally believed to prevent binding of the jack screw in the threads of the collector plate fitting. It also is generally believed that at least one guide pin and bushing are required in order to restrain rotation of the collector plate under torque supplied via the jack screw.
However, in practice, it has been found that the guide pins and bushings do not adequately ensure smooth and continuous motion of the collector plates toward and away from the side plates or each other.